1. Field of the Invention
The present invention generally relates to devices and techniques for guiding surgical needles. More particularly, the present invention relates to devices and techniques for percutaneously steering a surgical needle within a tissue medium.
2. Discussion of the Related Art
Accurate and precise needle insertion is an important aspect of many types of medical diagnoses and treatments. Accurate and precise needle placement is required in the treatment of afflictions including, for example, prostate cancer, liver cancer, and intracranial hemorrhage (ICH).
Needle biopsy for prostate cancer is performed on approximately 1.5 million men per year. A common treatment option is transperineal brachytherapy, which involves implanting thin needles to deposit radioactive seeds within the prostate. Precise placement of radioactive seeds is made difficult by organ deflection, dislocation and deformation. Further, significant seed placement error can occur if the needle is tangential to the prostate capsule wall upon penetration. This is generally due to the fact that the prostate's mechanical properties are considerably different from that of the surrounding tissue. According to the related art, needles for delivering radioactive seeds are substantially rigid. As such, accurate and precise needle insertion may be hampered by prostate deflection, dislocation, and deformation. The resulting inaccuracy may hinder optimal application of a radiation dose.
Hepatocellular (liver) cancer is one of the most common cancers in the world, and one of the deadliest. Liver tumors are often treated with thermal ablation administered at the tip of a needle inserted through the skin under the guidance of ultrasound imagery. Liver tumors often have very different mechanical properties than the surrounding tissue, similarly to the aforementioned difficulties in penetrating a prostate capsule. Accordingly, liver tumors are generally difficult to penetrate.
Thermal ablative treatment of liver cancer is further complicated by the typical need for multiple overlapping thermal treatments of a tumor. According to the related art, rigid thermal ablative needles must be removed and reinserted to penetrate the tumor from different angles.
Intracranial hemmorhage (ICH) occurs in roughly 10 to 20 persons out of 100,000. Untreated clot resolution generally takes two to three weeks, with a mortality rate of approximately 50-75%. Related art treatments involve introducing a needle (through a burr hole drilled in the skull) for injecting drugs. The burr hole is generally drilled by freehand. Depending on the surgeon's hand-eye coordination, the burr hole may be misplaced, thereby resulting in the needle path being off as much as 20-25 degrees. To compensate, the burr hole is generally made significantly larger than otherwise necessary, which can lead to technical and clinical complications. The larger burr hole is generally required because the needle is substantially rigid, and is not capable of being steered within the brain.
In all of the above cases, the needles are generally rigid and are typically inserted by hand. Any initial misplacement or misalignment of the needle requires that the needle be pushed through the tissue medium in such a way that the tissue medium is distorted. The mechanical properties of the tissue medium generally deflect the needle, complicating what is already an inaccurate and imprecise needle guiding approach. Further, any changes or anisotropy in tissue mechanical properties may deflect the needle in a manner that is unpredictable to the surgeon, exacerbating the problem of inaccurate and imprecise needle targeting.
Accordingly, there is a need for a steerable needle that may be used for diagnostic and treatment purposes, wherein the needle may be steered through tissues of varying mechanical properties substantially without distorting the tissue medium. In the exemplary case of prostate cancer treatment, there is a need for a needle that may be steered to an optimal prostate capsule penetration angle. In the exemplary case of liver cancer treatment, there is a need for a needle that can apply multiple overlapping thermal ablations to a tumor without having to remove and reinsert the needle. In the exemplary case of ICH treatment, there is a need for a needle that may be steered through brain tissue medium to accurately and precisely target a clot while compensating for inaccurate burr hole placement.